Various forms of windmills have been heretofore provided. Many windmills are constructed in the general form of propeller assemblies and such windmills are reasonably efficient in more than minimal winds, but their efficiency falls off greatly when they are subject to only minimal winds.
Some forms of propeller-type windmills have been constructed including improvement characteristics whereby their efficiency in minimal winds is increased. Such improvement characteristics include hollow hub portions and hollow blade portions opening into the hub portions and with blade tip air outlets opening in directions opposite to the directions in which the leading edges of the blades face. Accordingly, wind entering the hollow hub portion passes therefrom into the blades, along the latter and out of the tip of the blades. While this improvement characteristic does in fact enable propeller-type windmills to perform with greater efficiency in minimal winds, there still exists a need for improvement of efficiency for propeller-type windmills when operating in minimal winds.
Windmills including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 1,300,552, 1,666,517, 1,667,506, 1,862,846, 1,923,054 and 2,007,506.